1. Adderley, W.P., 1998. Vertisolic soils under agroforestry in northeast Nigeria. PhD thesis. University of Wales.
2. The influence of soil variability on tree establishment at an experimental agroforestry site in North East Nigeria;Adderley;Soil Use and Management,1997
3. Aitchison, P.J., Bawden, M.G., Caroll, D.M., Glover, P.E., Klinkenberg, K., De Leeu, P.N., Tuley, P., 1972. The land resources of North East Nigeria. Volume 1. The Environment. Land Resource Study 9. Series Editor Tuley, P. Directorate of Overseas Survey, Surbiton, Surrey.
4. Advances in Historical Ecology,1998
5. Travels and Discoveries in North and Central Africa. 3 vols.;Barth,1857